Solar Energy Control

ABSTRACT

A solar energy collection system includes a solar concentrator operative to direct a concentrated solar beam onto a solar receptor. A shutter plate is positioned between the solar concentrator and the solar receptor and is movable from an open position adjacent to the solar beam, to a closed position wherein at least a portion of the solar beam contacts a front face of the shutter plate and is blocked from contacting the receptor. A cooling circuit is operative to circulate a cooling fluid to remove heat from the shutter plate. A shutter drive is operative to move the at least one shutter plate from the open position to the closed position, and a shutter control is operative to stop movement of the shutter plate at a plurality of locations between the open position and the closed position.

This invention is in the field of solar energy systems and in particularcontrolling the energy received by a solar receptor such as a boiler,oven, or the like.

BACKGROUND

Considerable development is taking place in an attempt to efficientlyand effectively harness solar energy. One typical system involves acurved mirror shaped to gather and focus solar rays into a cone-shapedfocused solar beam. A solar receptor is placed near the apex of the coneand considerable heat can be generated in the receptor to perform adesired function that requires heat energy. The curved mirrors aretypically made up of an array of smaller flat mirror segments arrangedon a curved frame to achieve the focusing effect, and can be quitelarge, depending on the energy requirement of the receptor.

Such solar systems are generally placed in arid locations where the sunis reliably available so that the heat generated by the solar beam willbe at least substantially consistent. The solar receptors can includeboilers, thermal reactors, Stirling engines, and the like. A problemwith such systems is controlling the amount of heat energy received bythe solar receptor. For example a Stirling engine has no control thatcorresponds to a throttle whereby the energy supplied to the enginecorresponds to the load. When powering a Stirling engine with solarenergy from a mirror array, the solar energy supplied to the engine issubstantially constant, and so the load must be maintained at asufficient level to use all the solar energy supplied by the mirrorarray. If the load drops, the engine very quickly overheats and isdamaged. Similar overheating and damage can occur with other solarreceptors as well.

To provide a level of control, the flat mirror segments on the mirrorarray can be mounted such that they can be moved by an actuator.Controllers activate the actuators and pivot the mirrors to produce thefocused cone-shaped solar beam. The amount of energy received by thereceptor can thus be varied. Thus when overheating is detected themirror segments are moved out of focus to reduce the amount of energyreceived, such as when the load on a Stirling engine drops. Such systemsalso allow a receptor to be heated slowly by gradually bringing the flatmirror segments into focus until the maximum or desired energy isreceived. The movable mirror segments, actuators, and controls arecomplex and so these systems are very costly to build and maintain.

It is also known to prevent damage from overheating by moving a plateinto position to block the solar beam, or a portion thereof. Such platesare made from refractory materials in order to withstand the intenseheat of the solar beam, and are quite fragile and subject to damage fromthe elements.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a solar energycontrol apparatus that overcomes problems in the prior art.

The present invention provides, in a first embodiment, for use in asolar energy collection system comprising a solar concentrator operativeto direct a concentrated solar beam onto a solar receptor, a solarshutter apparatus adapted to be positioned between the solarconcentrator and the solar receptor to selectively block a portion ofthe solar beam. The apparatus comprises at least one shutter platemovable from an open position adjacent to the solar beam, to a closedposition wherein at least a portion of the solar beam contacts a frontface of the shutter plate and is blocked from contacting the receptor. Acooling circuit is operative to circulate a cooling fluid to remove heatfrom the shutter plate. A shutter drive is operative to move the atleast one shutter plate from the open position to the closed position,and a shutter control is connected to the shutter drive and is operativeto stop movement of the shutter plate at a plurality of locationsbetween the open position and the closed position.

The present invention provides, in a second embodiment, a solar energycollection system comprising a solar concentrator operative to direct aconcentrated solar beam onto a solar receptor. A shutter plate ispositioned between the solar concentrator and the solar receptor and ismovable from an open position adjacent to the solar beam, to a closedposition wherein at least a portion of the solar beam contacts a frontface of the shutter plate and is blocked from contacting the receptor. Acooling circuit is operative to circulate a cooling fluid to remove heatfrom the shutter plate. A shutter drive is operative to move the atleast one shutter plate from the open position to the closed position,and a shutter control is connected to the shutter drive and is operativeto stop movement of the shutter plate at a plurality of locationsbetween the open position and the closed position.

The present invention provides a solar control apparatus that prevents aportion of a focused solar beam from contacting a solar receptor. Theapparatus comprises a shutter movable from an open position, where thecomplete solar beam hits the solar receptor, to a closed positionwherein at least a portion of the solar beam is blocked and preventedfrom hitting the solar receptor. The apparatus can comprise one or moreshutter plates, each having a cooling conduit defined in an interiorthereof, and a source of cooling fluid connected to circulate throughthe cooling conduit to remove heat from the shutter plate. Thecirculating cooling fluid removes the considerable amounts of heatgenerated in the shutter plates, and dissipates same in a locationremote from the shutter plates, such as though a radiator or the like.

The present invention provides a shutter apparatus adapted to bepositioned between a solar concentrator, such as a curved mirror, thatis operative to focus solar rays into a focused solar beam, and a solarreceptor that is oriented to receive the focused solar beam. The solarreceptor will typically be a reaction chamber, Stirling engine, or thelike and the curved mirror will be provided by an array of mirrorsegments.

In one embodiment, the shutter apparatus comprises a plurality ofshutter plates pivotally mounted to a shutter frame, and a shuttercontrol operative to move the shutter plates from an open position,where the complete solar beam hits the solar receptor, to a plurality ofpartially closed positions wherein varying portions of the solar beamare blocked and prevented from hitting the solar receptor, and then to aclosed position where the solar beam is substantially blocked. Eachshutter plate includes an internal cooling conduit and a source ofcooling fluid is connected to each cooling conduit such that coolingfluid circulates through the cooling conduits to remove heat from theshutter plates.

In a second embodiment the shutter apparatus comprises an annularshutter plate defining a central aperture. Again the annular shutterplate includes one or more internal cooling conduits and a source ofcooling fluid is connected to the cooling conduits such that coolingfluid circulates through the cooling conduits to remove heat from theannular shutter plate. The annular shutter plate is mounted transverselyto the solar beam. When the annular shutter plate is located close tothe solar receptor, the complete solar beam can pass through the centralaperture and hit the solar receptor. As the annular shutter plate ismoved away from the solar receptor toward the curved mirror the outerportion of the cone-shaped solar beam hits the annular shutter plate andis thus prevented from hitting the solar receptor. Due to the conicalshape of the beam, the annular shutter plate can be wide enough thatwhen located a considerable distance from the solar receptor, the greatmajority of the solar beam is blocked, with only a small portion passingthrough the central aperture to hit the solar receptor. In thisembodiment a linear shutter control controls the distance between theannular shutter plate and the solar receptor.

The cooling fluid could conveniently and effectively be a mixture ofwater and glycol such as is used in engine cooling systems. Such amixture pumped in large volumes has the ability to remove a large amountof heat from the shutter plates, and is safe and convenient to handle.It is contemplated that other fluids, both liquid and gaseous, could beused as cooling fluids as well.

It is also contemplated that the shutter plates could be insulated orreflective on a rear surface thereof facing the solar receptor. Thenduring periods of cloud or at night, the shutter plates could be closedand heat would be retained in the solar receptor rather than radiatingout through the opening in the shutter apparatus.

DESCRIPTION OF THE DRAWINGS

While the invention is claimed in the concluding portions hereof,preferred embodiments are provided in the accompanying detaileddescription which may be best understood in conjunction with theaccompanying diagrams where like parts in each of the several diagramsare labeled with like numbers, and where:

FIG. 1 is a schematic side view of a shutter apparatus of the inventionset up between a solar concentrator, schematically illustrated as acurved mirror, and a solar receptor where the shutter apparatus is inthe open position with all of the solar beam being received by the solarreceptor;

FIG. 2 is a schematic side view of an embodiment of the shutterapparatus of FIG. 1 with shutter plates that are moved toward each otherto a partially closed position with only a portion of the solar beambeing received by the solar receptor;

FIG. 3 is a schematic side view of an alternate embodiment of theshutter apparatus of FIG. 1 with an annular shutter plate showing theshutter apparatus moved toward the solar concentrator to a partiallyclosed position with only a portion of the solar beam being received bythe solar receptor;

FIG. 4 is a perspective rear view of a shutter apparatus comprisingpivoting shutter plates such as could be used in the embodiment of FIG.2 showing the shutter plates in the open position;

FIG. 5 is a perspective front view of the shutter apparatus of FIG. 4showing the shutter plates in the open position;

FIG. 6 is a perspective rear view of the shutter apparatus of FIG. 4showing the shutter plates in partially closed position;

FIG. 7 is a perspective front view of the shutter apparatus of FIG. 4showing the shutter plates in an almost fully closed position, and alsoshowing a shield plate installed to protect the shutter controlmechanism;

FIG. 8 is a schematic perspective rear view showing the internal coolingconduit in one of the shutter plates;

FIG. 9 is a front view of an alternate annular shutter plate such aswould be used in the shutter apparatus of FIG. 3;

FIG. 10 is a schematic illustration of the operation of the shutterapparatus of FIG. 10.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1 schematically illustrates a shutter apparatus 2 of the inventionset up between a solar concentrator, illustrated as a curved mirror 4,and a solar receptor 6 such as are known in the prior art. The curvedmirror 4 focuses solar rays into a cone-shaped solar beam 8, and thesolar receptor 6 is positioned substantially at the apex of the cone toreceive the solar beam 8. The heat generated by the solar beam 8 in thesolar receptor 6 is used in various ways as are well known in the art.

In FIG. 1, the shutter apparatus 2 is shown in the open position whereall of the solar beam passes through the shutter apparatus and isreceived by the solar receptor 6. FIG. 2 schematically illustrates theoperation of an embodiment of the shutter apparatus 2 that uses aplurality of movable shutter plates to block the solar beam 8 andprevent varying portions thereof from hitting the solar receptor 6. FIG.2 illustrates the shutter apparatus 2 in a partially closed positionwith only a portion of the solar beam 8 being received by the solarreceptor 6.

An embodiment of a shutter apparatus 2 is illustrated in FIGS. 4-8 thatfairly evenly controls the solar energy received by the solar receptor6. The shutter plates 10 are pivotally mounted at one corner thereof toa shutter frame 12 and define a central aperture 14. The shutter plates10 are also pivotally connected at another corner thereof via links 20to a shutter ring 16 that rotates with respect to the shutter frame 12in response to rotation of a drive motor 18. Thus the shutter plates 6can pivot from the open position of FIGS. 4 and 5, through the partiallyclosed position of FIG. 6, and through the more fully closed position ofFIG. 7 to a substantially completely closed position.

It can thus be seen that as the shutter plates 6 move from the openposition to the closed position, varying portions of the solar beam 8will be blocked and prevented from hitting the solar receptor 6. Theheat energy received by the solar receptor 6, and thus the temperaturethereof, can be thus be finely controlled by activating the drive motor18 to open or close the shutter plates 10. As can be seen, unlike acamera shutter, the shutter plates 10 do not overlap. The solar beam 8can pass between the edges of the shutter plates 10, as well as throughthe center of the central aperture 14. FIG. 7 illustrates the front ofthe shutter apparatus 2 that faces the curved mirror 4 with a shieldplate 21 installed to protect the shutter mechanism. The illustratedembodiment thus closes off the conical solar beam 8 from all sidesthereof at once, such that the remaining portion of the solar beam 8received by the solar receptor 6 is substantially evenly distributed onthe face of the solar receptor 6, resulting in substantially evenheating of the receptor.

While the particular arrangement illustrated is simple and convenientand results in even heating of the solar receptor 6, it is contemplatedthat other arrangements would also serve the purpose of moving theshutter plates 10 in and out of the solar beam 8 to block reception bythe solar receptor 6. Such a shutter apparatus could be provided forexample by positioning a pair of shutter plates adjacent to each side ofthe beam 8 and moving them together or apart to block or not block thebeam 8. Such other arrangements are therefore contemplated to fallwithin the scope of the invention.

FIG. 8 schematically illustrates in one shutter plate 10 an internalcooling conduit 22 that is defined in the interior of each shutter plate10. The shutter plates 10 are quite thick, and the cooling conduit 22 isprovided quite simply in the illustrated embodiment by drilling a pairof holes 24 from the outer edge of the shutter plate 10 on an angletoward the inner ends thereof. The holes 24 meet near their inner endsand thus form the cooling conduit 22 where cooling fluid flowing intoone hole will also flow into the other hole. Hose barbs 26 are attachedto the exposed ends of the holes 24 to facilitate connection of thecooling conduit 22 to a cooling fluid source 28. A cooling fluid, suchas a water-glycol mixture, air, or the like is circulated from thecooling fluid source 28 through the cooling conduit 22.

The holes 24 are sized and positioned such that they pass quite close tothe surface of the shutter plate 10 to quickly draw heat away from thesurface. The shutter plates are made from material that conducts heatwell and also withstands exposure to the elements. Aluminum provides agood material for the shutter plates 10, however other materials such ascopper could also be used. The front face of the shutter plates 10,facing the curved mirror 4, could also be polished to reflect the solarbeam 8 such that less heat is absorbed that must be removed by thecooling fluid.

Further, where the shutter apparatus 2 is located closely adjacent tothe solar receptor 6 as in FIGS. 1 and 2, the shutter plates 10 could beinsulated or reflective on a rear surface thereof facing the solarreceptor 6. Then during periods of cloud or at night, the shutter plates10 could be closed and heat would be retained in the solar receptor 6rather than radiating out through the central aperture 14 and beinglost.

FIG. 9 schematically illustrates an alternate shutter apparatus 102,suitable for use as illustrated in FIGS. 3 and 10. The shutter apparatus102 comprises an annular shutter plate 110. One or more internal coolingconduits 122 are defined in the annular shutter plate 110 in a similarmanner to that described above and are connected to a cooling fluidsource. The annular shutter plate 110 is again made from heat conductivematerial to facilitate removal of heat by cooling fluid circulatingthrough the cooling conduits 122.

As illustrated in FIG. 10 when the annular shutter plate 110 is locatedin position A, close to the solar receptor 6, all of the solar beam 8passes through the central aperture 114 and hits the solar receptor 6.The annular shutter plate 110 is mounted on a track or the like suchthat the drive can move the shutter plate 110 toward or away from thesolar receptor 6. As the annular shutter plate 110 moves away from thesolar receptor 6 the outer portions of the conical solar beam 8 areblocked by the annular shutter plate 110. In position B, a small portionof the solar beam 8 is blocked, while at position C a very large portionof the solar beam 8 is blocked.

While the particular arrangements illustrated are simple and convenient,it is contemplated that other arrangements would also serve the purposeof moving the shutter plates 10, 110 in and out of the solar beam 8 toblock reception by the solar receptor 6, and such other arrangements arecontemplated to fall within the scope of the invention.

Thus the foregoing is considered as illustrative only of the principlesof the invention. Further, since numerous changes and modifications willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all such suitable changes or modificationsin structure or operation which may be resorted to are intended to fallwithin the scope of the claimed invention.

1. For use in a solar energy collection system comprising a solarconcentrator operative to direct a concentrated solar beam onto a solarreceptor, a solar shutter apparatus adapted to be positioned between thesolar concentrator and the solar receptor to selectively block a portionof the solar beam, the apparatus comprising: at least one shutter platemovable from an open position adjacent to the solar beam, to a closedposition wherein at least a portion of the solar beam contacts a frontface of the shutter plate and is blocked from contacting the receptor; acooling circuit operative to circulate a cooling fluid to remove heatfrom the shutter plate; a shutter drive operative to move the at leastone shutter plate from the open position to the closed position; and ashutter control connected to the shutter drive and operative to stopmovement of the shutter plate at a plurality of locations between theopen position and the closed position.
 2. The apparatus of claim 1comprising a plurality of shutter plates arranged such that the solarbeam passes between the shutter plates, and wherein the shutter drive isoperative to move the shutter plates toward each other to the closedposition and away from each other to the open position.
 3. The apparatusof claim 2 wherein the shutter plates are arranged substantially in aplane transverse to the solar beam and pivotally mounted on a shutterframe such that the solar beam passes through a central aperture formedby the shutter plates when in the open position, and wherein the driveis operative to pivot the shutter plates toward each other to the closedposition to reduce a size of the central aperture.
 4. The apparatus ofclaim 3 comprising a shutter ring rotatably mounted to the shutter frameand wherein the shutter plates are each pivotally mounted at a firstportion thereof to the shutter frame and are pivotally connected at asecond portion thereof to the shutter ring by a link, and wherein thedrive is operative to rotate the shutter ring with respect to theshutter frame to move the shutter plates from the open position to theclosed position.
 5. The apparatus of claim 1 wherein solar beam iscone-shaped and decreases in diameter between the solar concentrator andthe solar receptor, and wherein the at least one shutter plate defines acentral aperture, and wherein the at least one shutter plate is locatedin proximity to the solar receptor when in the open position such thatthe solar beam passes through the central aperture, and is moved towardthe solar concentrator to the closed position such that a portion of thesolar beam contacts the at least one shutter plate adjacent to thecentral aperture.
 6. The apparatus of claim 5 wherein the at least oneshutter plate is mounted on a track aligned between the solarconcentrator and the solar receptor, and wherein the drive is operativeto move the at least one shutter plate along the track.
 7. The apparatusof claim 1 wherein the cooling circuit comprises a cooling conduitdefined by at least one shutter plate and connected to a source ofcooling fluid.
 8. The apparatus of claim 7 wherein the cooling conduitcomprises a first hole extending from a first location on an outer edgeof the at least one shutter plate to an inner end located inside the atleast one shutter plate, and a second hole extending from a secondlocation on an outer edge of the at least one shutter plate to an innerend located inside the at least one shutter plate, such that the firstand second holes intersect, and such that cooling fluid circulated intothe first hole flows into the second hole.
 9. The apparatus of claim 8wherein the first and second holes are located in proximity to the frontface of the shutter plate.
 10. The apparatus of Claim 1 wherein thefront face comprises a reflective surface.
 11. The apparatus of claim 1wherein the at least one shutter plate is located in proximity to thesolar receptor, and wherein a rear face of the at least one shutterplate comprises one of a reflective surface and an insulation layer suchthat when in the closed position the at least one shutter plate isoperative to reduce heat loss from the solar receptor through the atleast one shutter plate.
 12. A solar energy collection systemcomprising: a solar concentrator operative to direct a concentratedsolar beam onto a solar receptor; a shutter plate positioned between thesolar concentrator and the solar receptor and movable from an openposition adjacent to the solar beam, to a closed position wherein atleast a portion of the solar beam contacts a front face of the shutterplate and is blocked from contacting the receptor; a cooling circuitoperative to circulate a cooling fluid to remove heat from the shutterplate; a shutter drive operative to move the shutter plate from the openposition to the closed position; and a shutter control connected to theshutter drive and operative to stop movement of the shutter plate at aplurality of locations between the open position and the closedposition.
 13. The apparatus of claim 12 comprising a plurality ofshutter plates arranged such that the solar beam passes between theshutter plates, and wherein the shutter drive is operative to move theshutter plates toward each other to the closed position and away fromeach other to the open position.
 14. The apparatus of claim 13 whereinthe shutter plates are arranged substantially in a plane transverse tothe solar beam and pivotally mounted on a shutter frame such that thesolar beam passes through a central aperture formed by the shutterplates when in the open position, and wherein the drive is operative topivot the shutter plates toward each other to the closed position toreduce a size of the central aperture.
 15. The apparatus of claim 14comprising a shutter ring rotatably mounted to the shutter frame andwherein the shutter plates are each pivotally mounted at a first portionthereof to the shutter frame and are pivotally connected at a secondportion thereof to the shutter ring by a link, and wherein the drive isoperative to rotate the shutter ring with respect to the shutter frameto move the shutter plates from the open position to the closedposition.
 16. The apparatus of claim 12 wherein solar beam iscone-shaped and decreases in diameter between the solar concentrator andthe solar receptor, and wherein the shutter plate defines a centralaperture, and wherein the shutter plate is located in proximity to thesolar receptor when in the open position such that the solar beam passesthrough the central aperture, and is moved toward the solar concentratorto the closed position such that a portion of the solar beam contactsthe shutter plate adjacent to the central aperture.
 17. The apparatus ofclaim 16 wherein the at least one shutter plate is mounted on a trackaligned between the solar concentrator and the solar receptor, andwherein the drive is operative to move the at least one shutter platealong the track.
 18. The apparatus of claim 12 wherein the coolingcircuit comprises a cooling conduit defined by at least one shutterplate and connected to a source of cooling fluid.
 19. The apparatus ofclaim 18 wherein the cooling conduit comprises a first hole extendingfrom a first location on an outer edge of the at least one shutter plateto an inner end located inside the at least one shutter plate, and asecond hole extending from a second location on an outer edge of the atleast one shutter plate to an inner end located inside the at least oneshutter plate, such that the first and second holes intersect, and suchthat cooling fluid circulated into the first hole flows into the secondhole.
 20. The apparatus of claim 19 wherein the first and second holesare located in proximity to the front face of the shutter plate.
 21. Theapparatus of claim 12 wherein the front face comprises a reflectivesurface.
 22. The apparatus of claim 12 wherein at least one shutterplate is located in proximity to the solar receptor, and wherein a rearface of the at least one shutter plate comprises one of a reflectivesurface and an insulation layer such that when in the closed positionthe at least one shutter plate is operative to reduce heat loss from thesolar receptor through the at least one shutter plate.